1. Field of the Invention
The present invention relates to access control systems, and more particularly pertains to a system utilizing optically readable key units.
2. Description of the Prior Art
Many of the shortcomings of existing access systems are related to the ease of duplication of keys or magnetic cards which provide access. Even elaborate systems utilizing fingerprint or retinal imaging can be circumvented by a clever hacker. Although no system can provide 100% security, all systems have various levels of security rated in estimated man hours to defeat the particular system. The higher the complexity of a system, the higher the access security as well as the cost. Electro-optical security systems represent one of the better known types having a high degree of complexity which thus results in a comparable degree of difficulty to circumvent. These systems are employed more frequently than fingerprint or retinal imaging, and cost substantially less to install and utilize. Accordingly, electro-optical security systems provide the most promise for improvement at minimal cost while increasing the level of difficulty associated with circumvention.
A typical example of an electro-optical lock system is to be found in U.S. Pat. No. 3,885,408 which issued to Charles Clark, Jr. on May 27, 1975. This patent discloses a finger operated electro-optical lock system in which an optical keyboard having at least one zone indicated thereon is illuminated by ambient energy until touched by the finger of a human hand, thereby blocking the radiant energy passing through the zone. A counter is then enabled to cycle a numeric display and when the first digit of the combination appears in the display, the finger is lifted and reapplied until the second digit of the combination is displayed. While being functional for its intended purpose, this system makes no use of a hand held key or magnetic card and thus requires the user to memorize the combination.
A more recent example of an optical key system is to be found in U.S. Pat. No. 4,079,605 which issued to Vernon Bartels on Mar. 21, 1978. The Bartel's patent is directed to an optical key reader for door locks and employs an optical scanning means for detecting a code pattern on a key unit. The detected code is compared by a comparator having a predetermined code which is stored in a reader, and if a match is found in this comparison, the comparator generates an actuation signal to allow access through a door. This type of system is the most desirable for seeking improvement since such improvement could possibly be accomplished at a minimum cost and accordingly there exists a continuing need for such improvements to provide greater access security. In this respect, the present invention substantially fulfills this need.